Error 721 and PPTPPING


B

Basil Copeland

I still haven't solved the problem with Error 721.

I've now a copy of the PPTPPING tools. I run PPTPSVR
and the machine I'm trying to connect to, and PPTPCLNT on
the machine I'm connecting from. Everything seems to work
the way it is supposed to: the server gets the message I'm
sending, and the client receives the servers response.

Shouldn't that mean that GRE traffic is flowing
through the linksys router just fine?

If so, then what's the problem?

-Basil
 
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B

Brian Oakes [MSFT]

Nope, all this means is TCP/1723 is working fine. There is still a good
change GRE 47 is being blocked on one of the devices.

There is a greping.exe and gresvr.exe as well to test.

--

Best regards,
Brian Oakes, MCSE
Microsoft Product Support
Windows 2000 Server Networking Team

This posting is provided "AS IS" with no warranties and confers no rights.
Please reply to the newsgroup so that others may benefit.
 
B

Basil Copeland

-----Original Message-----
Nope, all this means is TCP/1723 is working fine. There is still a good
change GRE 47 is being blocked on one of the devices.
Well, you are the expert, so I ought to believe what you
are telling me. But if you are right, then this is one
very misleading utility!

FWIW, I may have written in haste about the test showing
that everything was working as it should.

Here, for instance, is the output to the console from the
client side:

{BEGIN PASTE}

Initializing WinSock...
Obtaining host information...
Successfully resolved server's host information

======================================
Enter data to send to server (between 1 and 255 chrs.),
then hit enter:
-->Is this a test of GRE or not?

Successfully connected to server using TCP port 1723 (PPTP)
Sending data to server

Waiting for a reply to the data which was just sent...
Received a reply. Reply contains the following text:
---> Hello, there! This is a reply from the server.

=================================
Connectivity test to TCP Port 1723 was successful!!!
Closing down socket...
=================================

Creating a socket to test GRE protocol traffic...

Total GRE packets sent = 1
Total GRE packets sent = 2
Total GRE packets sent = 3
Total GRE packets sent = 4
Total GRE packets sent = 5

=====================================
Check server to see if the GRE packets were received
successfully
=====================================

Closing down socket

Goodbye!

{END PASTE}

And this is the response output from the server side:

{BEGIN PASTE}

Now you must run pptpclnt.exe on remote machine

Waiting for inbound connection on TCP port 1723...
Inbound connection from client has completed successfully!

Data received from the client:
----> Is this a test of GRE or not?

Sending the message 'Reply from Server' to the client

=====================================================
Connectivity test to TCP Port 1723 was successful!!!
Closing down socket...
=====================================================

Created socket for GRE protocol test

Listening on PROTOCOL 47 for incoming GRE packets...

{END PASTE}

I now see that there are TWO tests occuring here; one for
Port 1723, and the other for Protocol 47. And at this
point, the server doesn't appear to be receiving
anything. So this indicates that there IS a problem with
GRE packets getting through.
There is a greping.exe and gresvr.exe as well to test.
So why should I need this? It appears to me that pptpping
DOES test for GRE packets on Protocol.

Well, this is progress of sorts, in that I know a little
more than I did earlier. I just found another, very
cryptic linksys kb article that tells me to change the lan
side ip address of the router from the default 192.168.1.1
to 192.168.254.1. What the kb article DOESN'T say, which
could be confusing to the less informed, is that if one is
using static ip addresses (and the linksys docs say NOT to
use the router dhcp if using pptp passthrough!) is that
this will break all static tcp/ip settings behind the
router that are pointing to a gateway of 192.168.1.1. So
to test this I'm going to have to some further
reconfiguration.

Thanks for the feedback.

-Basil
 
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M

Marc Reynolds [MSFT]

Hi Basil,

Your results with PPTPping show that GRE is in fact blocked somewhere along
the path. If GRE were open the results you would see from PPTPping would
look like this:

{BEGIN PASTE}
pptpsrv

Now you must run pptpclnt.exe on remote machine

Waiting for inbound connection on TCP port 1723...
Inbound connection from client has completed successfully!

Data received from client:
---> abcdefghijklmnopqrstuvwxyz


Sending the message 'Reply from server' to the client

=====================================================
Connectivity test to TCP Port 1723 was susccessful!!!
Closing down socket...
=====================================================

Created socket for GRE protocol test

Listening on PROTOCOL 47 for incoming GRE packets...

Total GRE packets received = 1
Total GRE packets received = 2
Total GRE packets received = 3
Total GRE packets received = 4
Total GRE packets received = 5

======================================
GRE protocol test was successful!
======================================
Closing socket

{END PASTE}

To get your VPN working you need to find out which router is blocking GRE
and configure it to allow the GRE traffic.

Thanks,
Marc Reynolds
Microsoft Technical Support
 

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